Four senior ministers in the Abbott government have been assigned secret-service style protection amid an angry backlash over the federal budget, while a fifth minister is also receiving personal protection over the specific threats.

The unprecedented ramp-up in security measures has seen Treasurer Joe Hockey, Foreign Minister Julie Bishop, Education Minister Christopher Pyne and junior defence minister Stuart Robert assigned Close Personal Protection (CPP) officers from the Australian Federal Police in the month since the budget.

High-profile Immigration Minister Scott Morrison has also been assigned CPP teams in recent months, with his controversial portfolio said to be the reason for the decision to ramp up his protection, not the budget.

Treasurer Joe Hockey. Photo: Glenn Hunt

Senior government sources have admitted extent of the protection required is unusual.

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The elite CPP teams are trained to blend into crowds, wear civilian clothing and are fitted with discrete earpieces that allow them to remain in constant contact with each other while protecting the ''principal'' - the politician or diplomat they have been assigned to protect.

CPP are assigned on a full-time basis to protect Prime Minister Tony Abbott and the Israeli and US ambassadors, while convention dictates that the deputy prime minister receives personal protection when the prime minister of the day is overseas.

However, in just the last month close personal protection has been assigned to provide the highest level of security at a slew of public events.

■ Ms Bishop was assigned a CPP team before a visit to Sydney University on May 16, just three days after the budget. The Foreign Minister was confronted and jostled by angry students at the event, forcing her CPP team to intervene.

■ Mr Hockey was accompanied on May 19 by CPP officers when he made an appearance on the ABC's Q&A program, six days after the budget. Mr Hockey also had a protection detail assigned to his residence in Canberra around the time of the budget.

■ Mr Pyne was assigned CPP for an appearance at Sydney University's St Johns College on May 22. This was one of several occasions the Education Minister, who is driving controversial tertiary reforms, has needed to have CPP protection.

■ Mr Robert was assigned CPP for a visit to Canberra's Australian National University on May 29.

Federal police provide an assessment on ministers' forward programs to assess whether there is a threat or a risk and whether extra protection might be required.